Windscreen wiper drive device with a park position switch

ABSTRACT

A driving mechanism for a windscreen wiper having a park position switch. The park position switch includes a swivable contact bridge which is pivotally arranged on a pin in the bottom of the driving mechanism. A contact tag on the contact bridge is made of an electrically conductive plate, with the contact tags being formed by bends. The contact bridge is operated via cams on the worm-gear. The cams cooperate with switch flaps on the contact bridge that are equally formed by bends. Preferably, the switch is mounted in the bottom of the driving mechanism so that the contact banks to be contacted can also extend in the bottom of the case.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention is concerned with a driving mechanism forwindscreen wipers having a park position switch.

A driving mechanism of the afore-mentioned type has been described in EP398630 A2. The contact bridge is shown to be an element displaceablewithin the lid of the gear box, which, by means of cams provided on theworm-wheel, can be reciprocated between two positions. To that effect,the contact bridge comprises a web guided in a corresponding slot. Inthe prior art arrangement, it is difficult to lock the contact bridgeagainst dropping. Also, problems are encountered in generating acorresponding bias to place the contact bridge in adequate contact withthe counter-contacts.

SUMMARY OF THE INVENTION

It is, therefore, suggested by the invention that the contact bridge betiltably arranged on a pin within the case. In such an arrangement, thecontact bridge can be locked on the pin by means of a simple lockingring. Moreover, an adequate bias can be generated by providing a springbetween the contact bridge and the locking ring. Preferably, the contactbridge is made of a plate from which two contact tags are so bent thatthe closing edges of the tags slide on corresponding contact bankswithin the casing. The two contact banks, preferably, are arrangeddiametrically opposite the swivel axis and, preferably, are at an equaldistance from the swivel axis.

In order to enable the contact bridge to be swiveled, two switch flapsare bent from the plate, the bending edges of which are approximatelydisposed on lines extending through the pivot. The switching flapscooperate with cams on the driving rear wheel of the wiper gear. Theswitch flaps, preferably, are arranged on both sides of an imaginaryline between the contact legs.

It is of advantage, especially with gear boxes made of plastic material,to locate the switch in or on the box bottom, with the contact banks tobe contacted being guided in the bottom of the case and closing flushwith the inner side of the case bottom. The contact banks, on one end,are guided through the motor flange into the motor and, on the otherend, are guided in a plug housing arranged on the gear box. The pivotpin is integrally formed with the plastic box.

This arrangement involves the advantages that the contact bridge is easyto assemble and that the distances covered by the contacts during theoperating life of a driving mechanism are reduced over those ofconventional switches so that additional contact rivets can beeliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to two Figures in thedrawing, wherein:

FIG. 1 shows a driving assembly, partly in section and partly as a planview, with a park position switch and the associated shell; and

FIG. 2 is a sectional view taken along the line II—II.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the cup-shaped box 1 of a gear of a driving mechanism onwhich, laterally, a motor flange 2 is integrally formed. Located in thecup-shaped box portion is a worm-gear 3 which is quasi transparent,thereby affording a free view to the bottom of the box. The worm-gear 3is in communication with a driven shaft by which one or several wiperarms can be driven in an oscillating way. The anchor shaft 4 of anelectromotor flanged thereto extends through the center of the flange 2,with a worm 5 being molded to the anchor shaft 4 to mesh with thetoothing of the worm-gear 3.

The electromotor is a d.c. commutator motor provided with three brushesto which energy is supplied through contrast banks 10, 11, 12. As themotor is furnished with three brushes it can be operated in two speedphases I, II. To that effect, a first brush, through the contact bank12, is permanently connected to the basic potential of the voltagesupply. A second brush arranged diametrically opposite the first brushon the collector can be supplied with energy through another contactbank 11. In that case, the motor runs in speed phase I.

A third brush staggered over the second brush by a certain angle can beenergized via a third contact bank 10. If energy is supplied to themotor through this brush, it runs in speed phase II, with the number ofrevolutions of the motor in speed phase I being lower than that in speedphase II.

FIG. 1 conveys that the contact banks 10, 11, 12 extend in the bottom ofthe case and are flush with the inner surface of the bottom.

In order to enable the contact blanks 10, 11, 12 to be directly arrangedwithin the case it is, of course, necessary for the box to be made ofplastic material. Otherwise a corresponding plastic board carrying thecontact banks is to be placed on the bottom of the case.

One end of the contact banks 10, 11, 12 is respectively guided throughthe flange 2 into the interior of the motor where these ends aresuitably connected to the brushes of the motor in an electricallyconductive way. The illustration is highly schematical as the passage ofthe contact banks into the motor housing does not form a part of theinvention. The same applies to the other ends of the contact bankswhich, laterally, are moved out of the case 1, possibly leading to aplug housing integrally formed with case 1. This feature has not beenshown in any closer detail either as it does not form the actual subjectof the invention.

The drive wipers generally involves the following problem. After thedriver having switched off the wiper system, the motor is to be suppliedwith energy at least until the wipers are again in their park positionat the bottom edge of the windscreen.

To achieve this, a so-called park position switch is mounted in thedriving mechanisms for windscreen wipers, which is actuated by thedriving mechanism itself in such a way that the driving motor iscontinued to be supplied with energy until the wipers have reached parkposition, even if the master switch to be operated by the driver isalready in the “OFF” position.

In the present instance, the switch comprises a contact bridge 20pivotally located above the case bottom. The electrically conductivebridge includes two contact tags 21, 22 with the one contact tag 21,irrespective of the angular position of the contact bridge, contacting acontact bank 13. The other contact tag 22, depending on the angularposition of the contact bridge 20, either contacts bank 12 permanentlyin communication with the base potential of the supply voltage, oranother bank 14 permanently connected to the positive potential of thesupply voltage.

The contact bridge 20 will be operated (yet to be explained hereinafter)by means of two cams 30, 31 laterally protruding from the side face ofthe worm-gear 3 in the axial direction.

The driving mechanism is now supplied with energy via a master switch tobe actuated by the driver. The master switch includes a switch bridge 41able to accept three positions A, I and II. In position II, the switchbridge connects the positive pole of the voltage supply to the contactbank 10 so that the motor runs in speed phase II. In position I, theswitch bridge 41 connects the contact bank 11 to the positive pole ofthe supply voltage so that the motor runs in speed phase I.

In position A, the switch bridge 41 connects the contact bank 11 tocontact bank 13. Depending on the angular position of the contact bridge20, a connection to the positive pole or to the base potential of thesupply voltage has now been established. If there is a connection to thebase potential—which applies only if the wipers are in their parkpositions—the motor is short-circuited and the wipers are non-actuated.If the contact bridge 20 is in a second position, in which the contactbank 14 is connected to the contact bank 13, voltage is supplied to themotor, i.e., it continues to run until the cam 30 on the worm-wheel 3swivels the contact bridge 20 so that a connection is establishedbetween the contact bank 13 and the contact bank 12.

The contact bridge 20 is made of a plate of electrically conductivematerial which, in plan view, is approximately cross-shaped. Centrallyof the longitudinal section 23 of the cross is a bore 24 through whichis guided a pin 25 protruding from the bottom of case 1. The pin 25forms the swivel axis of the contact bridge 20.

The ends of the longitudinal section 23 are bent off so that contacttags 21, 22 are formed, the connecting edges of which are in directabutment with the contact banks 12, 13, 14. To that extent, contactrivets otherwise customary can be foregone as, due to the constructionof the invention, the distances covered by the contacts, within theoperating life of the driving mechanism are substantially reduced overconventional designs.

The bending edges of the flaps 21, 22 extend in a direction tangentialto an imaginary circle about the swivel axis of the contact bridge 20.

The transverse section 26 of the cross-shaped contact bridge 20 isformed as a partial circle about the swivel axis, with the ends thereofbeing equally bent off, forming switch flaps 27, 28 cooperating with thecams 30, 31 on the worm-gear 3. The bent edges of the switch flaps 27,28 extend approximately along an imaginary line through the swivel axis.The dimensions of the contact bridge 20 and the arrangement of the cams30, 31 are such that the respective one cams 30, 31 when pushing awaythe appertaining switch flap 27, 28 so swivels the contact bridge 20that the respective other switch flap 28, 27 is led into the path ofmovement of the respective other cams 31, 30 thereby reciprocating thecontact bridge 20 once with each rotation of the worm-gear 3.

The contact bridge 20 is attached to the pin 25 by means of a lockingring 33. Located between the locking ring 33 and the contact bridge 20is a helical spring 34 (or flexible spring) ensuring that the contacttags 21, 22 are forced onto the appertaining contact banks. As in thisform of embodiment, the lever arms for the contact bridges, 21, 22 areequal in size, so that equal contact forces are generated.

To explain again the way of operation of the park position switch, it isassumed that the motor is operated in speed phase II. The worm-gear 3rotates in the direction of arrow 35. The switch cam 31 has just forcedthe contact bridge 20 into the fully shown position, now passing alongthe switch flap 28. Now, if the master switch 40 is actuated by thedriver and the switch bridge 41 placed into position A, the energysupply to the motor is through the current conducting path, i.e., thepositive pole of the voltage supply, the contact bank 14, the contactbridge 20, the contact bank 13, the switch bridge 41 in position A andthe contact bank 11. Hence, the motor is operated in switch phase I withthe consequence that the worm-gear 3 further moves toward arrow 35 untilthe switch cam 30 gets into abutment with the switch flap 27 which is inits path of movement.

The afore-described position of the worm-wheel 3 corresponds to aposition of the windscreen wiper shortly before its park position. Infurther rotation, the contact bridge 20, in FIG. 1, is swiveled in aclockwise direction until the contact tag 22 leaves the contact bank 14,thereby discontinuing the energy supply to the motor. Due to the energyof movement stored in the drive, the motor continues to run, therebyfurther swiveling the contact bridge 20 until the switch flap 22 getsinto contact with bank 12 thereby causing a short-circuit at which themotor operates as generator and is quickly decelerated.

In the afore-described position, the switch cam 31 is directly ahead ofthe switch flap 28 shown in broken lines. Once current is again appliedto the motor, the contact bridge 20 is restored so that, when theelectromotor is switched off and the wipers are still in the swivelzone, and also after release of the master switch 40, energy can besupplied until the wipers have reached their park positions.

In conclusion, it should be noted that the park position switch of theinvention also solves the problem encountered once the wipers cannot beplaced to their parking position, for example, because snow hasdeposited on the windscreen which, in conventional switches, results inthe wiper arms getting loaded when the engine continues to run. As soonas the engine is switched off by actuating the park position switch, thevoltage stored in the wipers will cause the engine to restart so thatenergy is again supplied to the engine.

The afore-described situation will not occur with a park position switchof the type provided by the present invention because the cam 30, movingagainst the direction of the arrow 35, in that case, will only move awayfrom the contact bridge without reswitching it.

To prevent the edge of the contact tag, which changes over from onecontact bank to the other, from digging into the plastic material of thecase, a slide insulated over the other contact banks can be providedbetween the two contact banks in the path of movement of the contacttag. If the distance between the slide and the contact banks is selectedsmaller than the longitudinal extension of the closing edge of thecontact bank, it can be safeguarded that the same at least in part lieseither on a contact bank or on the slide.

What is claimed is:
 1. A driving mechanism having a gear wheel for awindscreen wiper with a park position switch having contacts fixedwithin one of a case and a lid thereof, and a contact bridge of the parkposition switch relatively displaceable in the case between twopositions, with the contact bridge being displaceable via cams on thedriving gear wheel of the driving mechanism, characterized in that thecontact bridge is pivotally located on a pin defining a swivel axis andsaid pin eccentrically located from the gear wheel within one of thecase and the lid thereof, and the contact bridge is integrally formed ofan elongate plate with two contact tags bent from the plate to formcontacts from the end edges.
 2. The driving mechanism according to claim1, characterized in that end edges arranged in approximately tangentialrelationship to an imaginary circle about the swivel axis.
 3. Thedriving mechanism according to claim 2, wherein an imaginary lineextending from one contact tag to the other contact tag defines a firstside and a second side with the imaginary line disposed therebetween andcharacterized in that two switch flaps are bent from the contact bridge,with one of the switch flaps located in the first side and the otherswitch flap located in the second side.
 4. The driving mechanismaccording to claim 3, characterized in that the pin is integrally formedwith the case of the driving mechanism, and that contact banks to becontacted by the contact bridge extend in a bottom of the case flushwith an inner surface of the case.
 5. The driving mechanism according toclaim 4, characterized in that the contact tags have end edges whichdirectly superpose and are moveable into operably contact with thecontact banks within the case through the swivel axis of the contactbridge.
 6. The driving mechanism according to claim 5, characterized inthat the contact bridge is locked by a locking ring on the pin, with aresilient element arranged in coaxial relationship to the pin betweenthe locking ring and the contact bridge to drive the end edges of thecontact bridge toward operable engagement with the contact banks.
 7. Ina driving mechanism having a gear wheel for a windscreen wiper with apark position switch having contacts fixed with respect to an innersurface of a case thereof, and a contact bridge of the park positionswitch rotatably displaceable in the case between two positions, withthe contact bridge being displaceable via cams on the driving gear wheelof the driving mechanism, the improvement comprising: a pin integrallyformed with the case of the driving mechanism, the pin eccentricallylocated with respect to the gear wheel within the case; the contactbridge pivotally located on the pin defining a swivel axis of thecontact bridge, the contact bridge integrally formed of a single,monolithic plate having two contact tags bent to form contacts from theend edges of the monolithic plate defining a U-shaped cross-section, theend edges arranged in approximately tangential relationship to animaginary circle about the swivel axis, the contact bridge locked by alocking ring on the pin with a resilient element arranged in coaxialrelationship to the pin between the locking ring and the contact bridgeto bias the contact bridge toward the inner surface of the case; andcontact banks to be contacted by the contact bridge extending in abottom of the case flush with an inner surface of the case, wherein theend edges of the contact tags are directly superposed and operablyengageable with the contact banks within the case.
 8. In a drivingmechanism for a windscreen wiper with a park position switch having abox with a first inner surface and an open side, a lid with a secondinner surface and securable to the box to close the open side, a gearwheel with a center axis and positioned within the box, the improvementcomprising: a pin integrally molded to one of the box and lid positionedeccentrically to the axis of the gear wheel; and a contact bridgemountable on the pin, and formed of a single, monolithic metal platewith a plurality of contact tags bent to extend outwardly from the platedefining a U-shaped cross-section between opposite end edges of theplate, the end edges forming contacts.
 9. A driving mechanism for awindscreen wiper with a park position switch comprising: an open endedenclosure having an aperture; a lid securable to an open end of theenclosure; a drive shaft penetrating the enclosure through the aperture,and having a shaft axis; a gear wheel having a center axis and cams, thegear wheel mountable to the drive shaft in the enclosure, such that thecenter axis is aligned with the shaft axis; a pin integrally mounted toone of the enclosure and the lid, such that a pin axis is located offsetfrom the center axis; and a contact bridge mountable on the pin, andformed of a single, monolithic metal plate with a plurality of contacttags bent to extend outwardly from the plate defining a U-shapedcross-section between opposite end edges of the plate, the end edgesforming contacts.
 10. The driving mechanism of claim 9 furthercomprising a biasing element mounted on the pin and engageable with thecontact bridge such that the biasing element urges the contact bridge ina direction parallel to the pin axis.
 11. The driving mechanism of claim10 wherein the pin is integrally mounted to the enclosure.
 12. Thedriving mechanism of claim 11 further comprising a locking ringmountable to the pin, such that the biasing element is positionedbetween the locking ring and the contact bridge.
 13. The drivingmechanism of claim 12 wherein the biasing element is a coil spring. 14.A driving mechanism for a windscreen wiper with a park position switchcomprising: a contact bridge formed by a single, monolithic metal platewith a plurality of switch flaps bent in a first direction and aplurality of contact flaps bent in a second direction, such that thefirst direction and second direction are substantially opposite from oneanother, the contact bridge mountable on a pin for rotational movementbetween two positions, and the plurality of switch flaps operablyengageable with cams on a gear wheel for driving the contact bridgebetween the two positions.